Georgia Institute of Technology Processing Sound Ranges Barb Ericson Georgia Institute of Technology July 2005.

Georgia Institute of Technology

Processing Sound Ranges

Barb EricsonGeorgia Institute of Technology

July 2005

Georgia Institute of Technology

Creating a Sound Clip

• To clip the “This” out of “This is a test”.– Determine where it starts and stops– Using the sound explorer:

• String file = FileChooser.getMediaPath(“thisisatest.wav”);

• Sound s = new Sound(file);• s.explore();

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Finding the End of the This

Position the bar

Get the index

Play before bar to check

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To Create a Sound Clip

• Create a new Sound object– Of the appropriate size

• Ending value – starting value + 1

• Loop from start to end (inclusive)– for (int x = start; x <= end; x++)

• Use getSampleValueAt(index)– And setSampleValueAt(index,value);

• Return the new sound object

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Clip Methodpublic Sound clip(int start,

int end){ // calculate the number // of samples int lengthInSamples = end - start + 1; Sound target = new Sound(lengthInSamples); int value = 0; int targetIndex = 0; int i = start;

// copy from start to end while (i <= end) { value =

this.getSampleValueAt(i);

target.setSampleValueAt( targetIndex, value); i = i + 1; } return target;}

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Challenge

• Create a clip of “is” from thisisatest.wav

• Determine where to start and end the clip

• Create the clip

• Write it to a file

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Returning a Value from a Method

• To return a value from a method– Include a return statement– The type of the thing being returned must

match the declared return type– The clip method declared that it returned a

Sound object– The return statement returned the target

Sound object– If the types don’t match you will get a compile

error

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Splicing Sounds Together

• Originally cut the sound tape into segments and then assembled them into the right order

• Easy to do digitally

• Copy more then one sound into a target sound– Track the source index and target index

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Splice Methodpublic void splice(){ Sound sound1 = new Sound(FileChooser.getMediaPath(“guzdial.wav”)); Sound sound2 = new Sound(FileChooser.getMediaPath("is.wav")); int targetIndex = 0; // the starting place on the target int value = 0; int i = 0; // copy all of sound 1 into the current sound (target) while (i < sound1.getLength()) { value = sound1.getSampleValueAt(i); this.setSampleValueAt(targetIndex,value); i = i + 1; } // NOW WHAT?

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Reversing a Sound

• To reverse a sound– Create a copy of the original sound

• Sound orig = new Sound(this.getFileName());

– Then loop starting the sourceIndex at the last index in the source and the targetIndex at the first index in the target

• Decrement the sourceIndex each time• Increment the targetIndex each time

100 | 200 | 300 | 400 | 500

100 | 200 | 300 | 400 | 500 sourceIndex

targetIndex

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Reversing Method

public void reverse()

{

Sound orig = new Sound(this.getFileName());

int length = this.getLength();

// loop through the samples

}

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Reverse Part of a Sound Exercise

• Reverse just the second half of a sound– Start the targetIndex at the length / 2– Start the sourceIndex at the length – 1– Loop when the targetIndex < length

100 | 200 | 500 | 400 | 300

100 | 200 | 300 | 400 | 500 sourceIndex

targetIndex

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Mirror a Sound

• Copy the first half of the sound to the second half – And reverse the sounds in the second half– This is very similar to mirroring a picture

• Calculate the midpoint (length / 2) • Start the index at 1 and copy from midpoint – i to

midpoint + i• While index < midpoint

100 | 200 | 300 | 400 | 500

100 | 200 | 300 | 200 | 100

midpoint

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Mirror Sound Methodpublic void mirrorFrontToBack(){ int length = this.getLength(); // save the length int mirrorPoint = length / 2; // mirror around this int value = 0; // hold the current value int i = 1; // loop from 1 to mirrorPoint while (i < mirrorPoint) { value = this.getSampleValueAt(mirrorPoint-i); this.setSampleValueAt(mirrorPoint+i,value); i = i + 1; }}

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Mirror Back to Front Exercise

• Write a method to mirror from the back to the front– Copy the back half of the sound reversed to

the front

100 | 200 | 300 | 400 | 500

500 | 400 | 300 | 400 | 500

midpoint

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Blend Sounds

• How do we blend two sounds?– Copy the first 20,000 values of sound1– Copy from both by adding .5 * sound1 value

and .5 * sound2 value– Copy the next 20,000 values of sound 2

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Blend Sounds Methodpublic void blendSounds() { Sound sound1 = new Sound(FileChooser.getMediaPath("aah.wav")); Sound sound2 = new Sound(FileChooser.getMediaPath("bassoon-

c4.wav")); int value = 0;

// copy the first 20,000 samples from sound1 into target

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Testing Blend Sounds

• String fileName = FileChooser.getMediaPath(

"sec3silence.wav");

• Sound target = new Sound(fileName);

• target.explore();

• target.blendSounds()

• target.explore();

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Modify Blend Sounds Exercise

• Create another blendSounds method– That takes the file name of the sounds to

blend– And a value to start the blend at and another

to stop the blend at– Modify the original blendSounds method to

call this one

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Overloading Methods

• You can have several methods with the same name– As long as the parameter list is different

• In number of parameters• And/or types of parameters

– blendSounds()– blendSound(String name1, String name2, int

startBlend, int endBlend)

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Changing the Sound Frequency• The frequency of a wave

is the number of cycles per second (cps), or Hertz (Hz)– (Complex sounds have

more than one frequency in them.)

• Our perception of pitch is related (logarithmically) to changes in frequency– Higher frequencies are

perceived as higher pitches– We can hear between 5 Hz

and 20,000 Hz (20 kHz)– A above middle C is 440

Hz

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Double the Frequency

• If we take every other sample we double the frequency of the sound– Completes two cycles instead of one in the

same time– It will sound higher

100 | 200 | 300 | 400 | 500 100 | 300 | 500 | 0 | 0

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Double Frequency Method

public void doubleFreq(){ // make a copy of the original sound Sound s = new Sound(this.getFileName()); /* loop and increment target index * by one but source index by 2, * and set target value * to the copy of the original sound */

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Change Frequency Exercise

• Write a method that will copy each sound value 4 times to the target– Will the new sound be higher or lower?

• Can you make this more general?– By passing in the number of times to copy the

source value– Try it with 3 times and check the index values

to make sure that you are doing it right